<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button onclick="fn()">按钮</button>
  <div id="box" class="box section">box</div>
  <script>
    var div = document.querySelector('#box')
    function fn () {
      // div.innerHTML = 'box2'
      // 会解析标签
      // div.innerHTML = '<b>box3</b>'
      // 就不会解析标签
      div.innerText = '<b>box3</b>'

    }
  </script>
</body>
</html>